Police in Portland, Oregon, arrested at least 13 people Saturday, established concrete barriers, closed streets and bridges, and seized a multitude of weapons in an attempt to preempt violence between right-wing groups and anti-fascist counter-protesters.

Metal poles, bear spray, shields and other weapons were taken from protesters by the authorities Saturday as hundreds of far-right protesters and counter-demonstrators crowded the downtown area, but there were no major incidents between the two factions.

Portland Mayor Ted Wheeler said at an evening news conference, however, that the event was connected with “a rising white nationalist movement” and a growing sense of fear in the U.S.

The mayor said Joe Biggs, the organizer of the far-right demonstration, was not welcome in Portland. “We do not want him here in my city. Period.”

Biggs said Saturday was a success. “Go look at President Trump’s Twitter,” he told The Oregonian/OregonLive. “He talked about Portland, said he’s watching antifa. That’s all we wanted.”

U.S. President Donald Trump indicated Saturday morning that he could take action on Antifa. The president said in a tweet, “Major consideration is being given to naming ANTIFA an “ORGANIZATION OF TERROR.” Portland is being watched very closely. Hopefully the Mayor will be able to properly do his job!” However, there is no federal criminal offense of ‘domestic terrorism.’

Portland police used officers on bikes and in riot gear to keep black clad, helmet and mask-wearing anti-fascist protesters — known as Antifa — from following the right-wing groups. Hundreds of people remained on downtown streets.

Flag-waving members of the Proud Boys and Three Percenters militia group had gathered late in the morning, some also wearing body armor and helmets. Police said they had seized the weapons as the protesters assembled along the Willamette River that runs through the city.

Biggs, the organizer of the rally, is a member of the Proud Boys, which has been designated as a hate group by the Southern Poverty Law Center. Joining them were the American Guard, Three Percenters, Oathkeepers and Daily Stormers.

According to the Southern Poverty Law Center, the American Guard is a “white nationalist group,” Three Percenters and Oathkeepers are “extremist,” anti-government militias, and the Daily Stormers are “neo-Nazis.”

Countering the right-wingers was Portland’s Rose City Antifa, a local anti-fascist group that called on its members to take to the streets in an opposing rally.

More than two dozen local, state and federal law enforcement agencies, including the FBI, were in the city for the right-wing rally that reportedly drew people from across the country. Portland Police said all of the city’s 1,000 officers were on duty for the gathering that was publicized on social media and elsewhere for weeks.

Antifa has grown more visible recently and experts say the groups are not centrally organized, and their members may espouse a number of different causes, from politics to race relations to gay rights. But the principle that binds them — along with an unofficial uniform of black clothing and face masks — is the willingness to use violence to fight white supremacists, which has opened them to criticism from both left and right.